A non-volatile MRAM is adapted to store information in the magnetization of an array of memory bit cells. Such a conventional MRAM or MRAM device consists of a two-dimensional array of Magnetic Tunnel Junctions (MTJ), the memory bit cells, interconnected via word lines and bit lines. A conventional MTJ consists of two ferromagnetic layers separated by a thin dielectric tunnel barrier layer. One of these two ferromagnetic layers functions as a permanent magnet, the so-called fixed ferromagnetic layer or fixed layer. On the other side, the magnetization of the other layer, the so-called free magnetization layer or free layer, can be rotated by applying an external magnetic field, for example. The tunnel magneto resistance of the MTJ depends on the relative alignment of the magnetization of the free layer and the fixed layer. For addressing a single memory bit cell during a read operation, a one-dimensional selection scheme may be used (see reference [1]). For example, a read operation is accomplished by measuring the electrical resistance of a memory bit cell.
An alternative architecture for reading said memory bit cells consists in connecting each memory bit cell in the matrix using bit lines and word lines. Such a scheme is described in reference [2], for example. Further, in reference [3], a radiation effects assessment of MRAM devices is described.
Furthermore, referring to reference [4], thermally assisted writing in an MRAM device is shown. In reference [5], magnetic domain walls in constrained geometries are discussed.
Further, document US 2005/0242384 A1 describes a magnetic memory device comprising a magneto-resistance effect element that is provided at an intersection between a first write line and a second write line. Further, the magneto-resistance effect element has an easy axis that extends in a direction of extension of the first write line, and a first conductive layer for electrical connection to the magneto-resistance effect element, the first conductive layer having sides which are in flush with sides of the magneto-resistance effect element.
Moreover, document U.S. Pat. No. 7,245,524 B2 describes a magnetic memory device including a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction, and a magneto resistive element which is arranged at an intersection between the first and second write wirings, has a fixed layer, a recording layer, and a magneto resistive layer sandwiched between the fixed layer and the recording layer, and has an axis of easy magnetization obliquely with respect to the first and second directions, the recording layer including a first ferromagnetic layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first and second ferromagnetic layers, in which first magnetization of the first ferromagnetic layer and second magnetization of the second ferromagnetic layer are ferromagnetically coupled, and a ferromagnetic-coupling constant C of a ferromagnetic coupling is 0.0001 erg/cm2≦C≦0.2 erg/cm2.